Frequency responsive apparatus



Oct. 19, 1965 R. 0. HAWKINS FREQUENCY nnsrousrvn APPARATUS 2 Sheets-Sheet 1 Filed April 4. 1962 FIG.1.

FIBER VIBRATION VIBRATOR INVENTOR. ROBERT D. Haw/(ms BY A r ramvgr SUMMING DEVICE PEAK DETECTOR PEAK DETECTOR PEAK DETECTOR FlG.2d.

.SSIE

"all

2 Sheets-Sheet 2 SOUND 1; VOLUME souuo 2; VOLUME "0" INVENTOR. 56 Raamr DHAWK/Ns (Jet. 19, 1965 Filed April 4, 1962 FIG .40.

ATTORNEY Fl b.

VIBRATOR United States Patent 3,213,197 FREQUENCY RESPONSIVF. APPARATUS Robert D. Hawkins, Greenlawn, N.Y., assignor to Sperry Rand Corporation, Great Neck, N.Y., a corporation of Delaware Filed Apr. 4, 1962, Ser. No. 185,064 17 Claims. (Cl. 179-1 This invention relatesto signal responsive apparatus and more particularly to apparatus having particular sensitivity to signals on the order of audio frequencies.

By means of a small light-conducting fiber, photoconductor, and cooperating mask and transparency, a modulating filter may be provided simply. The fiber is secured at one end in an opaque base in such a way that the tip of the secured end is exposed. Light is directed down the fiber to the mask and, when the base is vibrated at the resonant frequency of the fiber, the fiber moves from the shadow of the mask and directs the light through the transparency to the photoconductor. The size of the mask determines the threshold characteristics of the filter since it determines the magnitude of vibration necessary to take the fiber from the aforesaid shadow; the size of the transparency determines the limiting characteristics of the filter since it allows light to strike the photoconductor only when the displacement of the fiber from the mask shadow is small enough to allow light to pass through the transparency. Modulation results by varying the sizes and shapes of the mask and transparency in a manner to be described later.

One aspect of the present invention is that it may be expediently employed for example in sound or other compiex multifrequency signal responsive apparatus (which are useful in sound coded equipment and voice operated machinery in general, and the like) the operation of which is based on the following fact:

with the volume, i.e. intensity. of sound (or as the case may be, the intensity of the multifrequency signal) held to a substantially constant level, the various frequency components of a particular sound (or signal) have particular peak amplitudes, the sum of which is also particular; therefore, if a limiter is provided for each of the aforesaid frequency components and set to provide an output signal proportional to the amplitude of its respective component so long as the amplitude of that component is at or below its aforementioned particular peak amplitude, the sum of the output signals from the limiters will have a particular maximum for only the sound (or signal) in question.

A corollary of this fact is that the sum of the time integrals of the limiter output signals is also maximum for the particular sound (or signal) in question. For ease of description, the instant apparatus is described in a sound environment.

One apparatus operating according to the foregoing fact is provided with a multiplicity of tiny fibers of varying lengths, i.c. varying resonant frequencies, which are embedded in an opaque block, each in the manner of the aforementioned filter fiber. Then fiber masks and transparencies are provided for limiting 'purposes as follows: a photographic film is exposed to light passing through the fibers when none is in motion, developed to produce a negative, and then used to mask the lightemitting fiber ends. A second photographic film is laid over the negative and the fibers are set in motion by a suitable vibrator in response to a particular sound. Depending on which, and how much. the fibers vibrate, the second film is exposed to light; by making a positive from the exposed second film, limiting tranparencies (which are black at their centers and get progressively clearer near their ends) are provided. Now, according to the above fact, maximum light will pass through the transparencies only when the fibers move as they did when the second film was exposed.

A principal object of the invention is to provide a frequency filter.

Another object of the invention is to provide a modulating filter utilizing a light conducting fiber.

Another object of the invention is to provide apparatus .that is substantially responsive to only one multifrequency signal.

The invention will be described with reference to the figures wherein:

FIG. 1 is a schematic presentation of a filter embodying the invention;

FIGS. 20 through 20 are diagrams showing how various modifications may be made to the apparatus of FIG. 1;

FIG. 3 is a diagram in block form of a circuit responsive to a particular sound;

FIGS. 4a, 4b and 4c are diagrams useful in describing the invention;

FIG. 5 shows a side view of a presently preferred form of sound-responsive apparatus; and

FIG. 6 shows speech recognizing apparatus employing the invention.

Referring to FIG. 1, an opaque base 10 supports a light-conducting fiber 12, the end 14 of which is adapted to be exposed to a source of light. The fiber 12 may conduct light by either reflection or refraction, reflectiontype fibers being transparent mirror coated strands and refraction-type fibers being transparent strands of very high refractive indices compared to its surrounding medium. Light entering the fiber end 14 emerges at the fiber end 18 and impinges on a mask 16 having, in this form of the invention, an area which causes all light to be blocked whenever the fiber is stationary or bends in a particular direction. The mask 16 is on an otherwise transparent plate 20. A photoconductor 22, the resistance of which decreases when light falling thereon increases, serves to provide cathode resistor bias for a vacuum tube 24. The block 10, plate 20 and photoconductor 22 are contained within an opaque case 26 which in turn is secured to a suitable vibrator 28, e.g. a piezoelectric crystal cut to have a resonant frequency substantially dilferent from the resonant frequency of the fiber which, at least. can produce vibrations at the resonant frequency of the fiber. (If desired, a plurality of differently tuned filters may all be driven simultaneously by the same vibrator.)

When the vibrator 28 vibrates at a freqeuncy other than the resonant frequency of the fiber 12, the fiber remains substantially stationary and has its emitted light blocked by the mask 16. However, when the vibrator 28 vibrates at the resonant frequency of the fiber 12, the fiber is set sympathetically into motion and departs periodically from behind the mask 16, thereby causing light falling on the photoconductor 22 to be modulated at the fiber frequency of vibration. (See FIG. 2a.) As a result the resistance of the photoconductor 22 varies at the frequency of the vibrating fiber and causes the tube 24 to provide an output signal at that frequency.

FIGS. 2b through 20 show the manner and effect of several (but certainly not all) modifications to the light transmission path between the fiber end 18 and the photoconductor 22. In HG. 2b. a mask 16b (which is somewhat like the mask 16 of HO. 1, but larger) creates a threshold which must be exceeded by bending the fiber in the direction d bef re any light can impinge on the photoconductor. ln HG. 2c. a transparency 17 is combined with the mask 16 and, by causing the fiber 12 to vibrate to its extremes, two bursts of light strike the photoconductor 22 every other half cycle of the fiber vibration. FIG. 2d shows a mask 16c that ranges from black at one end to clear at the other which causes the photoconductor resistance to vary sinusoidally when the fiber l2 vibrates. FIG. 20 shows how frequency multiplication may be provided by the mere use of a plurality of masks which chop the light emitted by the fiber 12.

Referring to FIG. 3, apparatus adapted to operate according to the aforementioned fact has a signal representative of sound applied from a lead 40 to a plurality of filters 42 to break that signal into its respective frequency components. The filter output signals are applied then to respective limiters 44 and thence to peak detectors 46, e.g. the detector shown and described in the Radiation Laboratory Series, Waveforms, volume XIX, McGraw- Hill Book Company, Inc., New York, page 503. The peak detectors have their output signals applied to a summing device 48, the output signal of which drives the pointer of a meter 50 having an index 52. Each limiter. 44 is set to provide an output signal which can never exceed in amplitude the amplitude of its respective frequency component when that component is derived from a particular sound. The index 52 represents the pointer deflection when the signal applied to the lead 40 is representative of the particular sound in question.

FIG. 40 shown only (for ease of description) three components, A, f f having respectively amplitudes 3, 2 and l, of the particular sound for which the limiters 44 are set. The limiter adapted to receive the I filter output signal is set to pass any signal having an amplitude less than 3; the limiter adapted to receive the f; filter output signal is set to pass any signal having an amplitude less than 2, etc. The peak detectors, therefore, respectively produce output signals representing the signal amplitudes 3, 2 and I. With peak amplitude signals 3, 2 and I applied to the summing device 48, an output signal representing the sum 6 is produced which drives the meter 50 pointer accordingly, i.e. whenever the meter has a reading of 6 (which constitutes the index 52), the lead 40 has impressed thereon a signal representing the sound for which the limiters 44 were set.

FIG. 4b shows the f and f frequency components of a different signal represented sound of the same intensity as the sound of FIG. 4a, i.e. the total areas under all if a signal representing the sound of FIG. 4b is applied to a device like that shown in FIG. 3, such device being Set as above for the sound of FIG. 4a, the frequency comonent f will be allowed to pass through its respective limiter unaltcrcd, but the'f component will be held to an amplitude of l by the action of its respective limiter.

As a result, the peak detector detects a peak amplitude of l and the f peak detector detects an amplitude of .5, the sum of which is substantially less than 6 as occurred in the siutation depicted in FIG. 4a.

FIG. shows a particular sound responsive device that operates according to the foregoing fact corollary, but in an improved way, i.e. instead of providing continual integration, the apparatus of FIG. 5 provides signal component integration only so long as such signals do not have respective amplitude limits exceeded. Fibers, designated by the numerals 54. of varying lengths are supported by an opaque base 56. The ends of the fibers which are supported by the base 56 are adapted to be exposed to a source of light. Masks 58 are provided for each of the fibers and are provided as hcrcbcfore mentioned, i.e. by exposing a photographic film to light emanating from the fibers and producing a negative 57 therefrom. Transparencies 60 (a. I, etc) are also provided by the photographic pr cess hercbcfore mentioned, i.e. by exciting certain fibers to vibration and making a 4 positive 59 from a photographic film exposed to the light that they emit. A photoconductor 62 is then secured to receive whatever light passes through the transparencies. A broadband vibrator, e.g. a piezoelectric crystal cut to have a resonant frequency well above the highest fiber resonant frequency, is adapted to receive a sound representative signal and accordingly set the base 56 in motion.

With transparencies 60a, b and 0 provided respectively for the frequency components f f and of FIG. 4a, i.e. with the lengths of those transparencies being respectively proportional to amplitudes 1, 2 and 3, the fibers 54a, 54b and 540, when set into motion, direct light through their respective transparencies to the photoconduetor 62. So long as the f f and f signal components have amplitudes less than 3, 2 and 1, all light which gets by the negative 57 reaches the photoconductor 62; that is, peak light reaches the photoconductor 62 whenever the frequency components f f and f all have the amplitudes shown in FIG. 4a, thereby causing the integration of that light to peak also.

For a sound having the frequency components depicted in FIG. 4b, the light reaching the photoconductor will be proportional to the areas under the curves of FIG. 40, this being, by inspection. obviously far less than that which reached the photoconductor in the situation described immediately above. The f; frequency component of FIG. 4b causes the fiber 54a to remain always within the limits of the transparency 60a; the frequency component f causes the fiber 54b to be usually outside the limits of its transparency 60b (spending but a short duration within the border of the transparency); the fiber 54c remains stationary and has all its light blocked by its respective mask 58. As a result, all light emitted by the fiber 54a and only a small part of the light emitted from the fiber 54b reaches the photoconductor 62, i.e. the the apparatus of FIG. 5 when receiving a signal representing the sound of FIG. 4b, has practically no output signal if its masks and transparencies are set for the sound of FIG. 4a.

FIG. 6 shows a device that produces a substantial output signal only when a signal representative of a particular complex sound, e.g.' two syllables, is applied to a broadband vibrator 80. The vibrator 80 has associated therewith two devices 82 and 84, like the device of FIG. 5, which are so cascaded that the device 84 is enabled only when the device 82 provides an output signal, i.e. each device 82 and 84 has its own light source, respectively designated 86 and 88, with the source 88 being energized when the device 82 actuates a relay circuit 90. Only for a particular combination of syllables are both devices 82 and 84 responsive, with the device 84 producing ultimately the output signal mentioned above.

While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than of limitation and that changes within the purview of the appended claims may he made without departing from the true scope and spirit of the invention in its broader aspects.

What is claimed is:

1. Apparatus responsive to vibratory motion comprising a light conductive fiber one end which is adapted to be illuminated by a source of light, signal producing means adapted to receive light from the other end of said fiber and produce a signal proportional thereto, mask means positioned between said fibers other end and said signal producing means, and means for vibrating said cally on said signal producing means.

2. Apparatus responsive at a particular frequency comprising a light conducting fiber adapted to transmit therethrough substantially all light introduced at one end to its other end, means supporting the fiber at one end, means for introducing light to the supported end of said fiber, means adapted to vibrate said fiber at its resonant frequency, mask means positioned in the fiber plane of vibration, said mask means being dimensioned to interpect periodically the light emanating from the free end of said fiber depending on whether said fiber vibrates with an amplitude above or below a certain amount, and signal producing means adapted to receive the light from said fibers free end responsive to produce an output signal in proportion thereto.

3. The apparatus of claim 2 wherein said fiber conducts said light by refracting it continually inward.

4. Apparatus for selectively converting a mechanical vibration to an electrical signal comprising a fiber, an opaque base supporting said fiber at one of its ends in a way that has the supported end exposed, means adapted to shine light down said fiber, said fiber being adapted to conduct its contained light by continually retracting it inward, a photoelectric element adapted to receive the light emitted from said fiber, vibration producing means secured to said base whereby said fiber vibrates at its resonant frequency when said base is subjected to vibrations at that frequency, and a mask positioned between the free end of said fiber and the photoelectric element in the fiber plane of vibration, said photoelectric element producing an electrical signal proportional to its received light.

5. Apparatus substantially responsive to only one particular multifrequency signal of a given intensity comprising a plurality of filters each adapted to receive a multifrequency signal said filters being responsive to different frequency components of multifrequency signals, respective limiters for each filter adapted to receive the filter output signals, said limiters preventing their respective output signals from exceeding in amplitude the amplitudes that they have when the received signal is the particular multifrequency signal in question, peak detector means responsive to produce signals respectively proportional to the amplitudes of the output signals from said limiters, means summing all said signals proportional to said amplitudes, and means indicating when said sum signal has a certain value.

6. Apparatus that produces a substantial output signal in response to only one particular multifrequency signal, comprising a plurality of filters each adapted to receive a multifrequency signal, said filters being responsive to diflerent frequency components of multifrequency signals, respective limiters for each filter adapted to receive the filter output signals, said limiters preventing their respective output signals from exceeding in amplitude the amplitudes that they have when the received signal is the particular multifrequency signal in question, peak detector means responsive to produce signals respectively proportional to the amplitudes of the output signals from said limiters, and means summing all Saidsignals proportional to said amplitudes to produce an output signal.

7. Apparatus that substantially responds only when a particular multifrequency signal is applied thereto comprising a base, a plurality of light conducting fibers of varying lengths, each being supported at one end by said base, a photoelectric element, means providing masks for each of said fibers that prevent light emitted at the free ends of their respective fibers from reaching said photoelectric element when those fibers do not move relative to their masks, means adapted to receive signals and vibrate accordingly said base, means providing transparencies spatially aligned with the masks of the fibers that vibrate when the signal applied to said vibration means is the particular multifrequency signal in question, each of said transparencies being adapted to transmit light from its respective fiber when the fiber bends in its vibratory plane by any amount less than the maximum vibratory amplitude of that fiber for the particular multifrequency signal in question, said photoelectric element being adapted to receive the light passing through said transparencies and accordingly change its characteristics to produce a substantial indication only when the signal applied to said vibration means is the particular multifrequency signal in question.

8. Apparatus that provides a discrete output signal for only one particular applied multifrequency signal comprising support means, a plurality of light transmitting fibers of varying resonant frequencies, means adapted to receive signals and vibrate accordingly said. support means, whereby said fibers vibrate at their resonant frequencies when the received signal contains frequency components at those frequencies, mask means for each fiber dimensioned to block and pass light transmitted from its respective fiber depending on Whether that fiber vibrates with an amplitude above or below the amount by which that fiber vibrates when said particular multifrequency signal is applied to said vibration means, and means responsive to produce a signal proportional to the light passing said mask means.

9. Apparatus that provides a substantial output signal for only one particular multifrequency signal comprising support means, a plurality of light conducting fibers of varying resonant frequencies, means adapted to receive signals and vibrate accordingly said support means, whereby said fibers vibrate at their resonant frequencies when the received signal contains frequency components at those frequencies, means for each fiber adapted to block light emanating therefrom when its respective fiber is stationary, transparencies for those fibers that move when said particular multifrequency signal is applied to said vibration means which permit light from those fibers to pass theerthrough, said transparencies being progressively transparent from their centers to their extremities and being adapted to pass light from the fibers only so long as their respective instantaneous amplitudes of vibration are less than their peak vibratory amplitudes when vibrating in response to said particular multifrequency signal, and photoelectric means receiving the light passing through said transparencies and being responsive to produce a substantial output signal for only the particular multifrequency signal.

10. Apparatus responsive to produce a discrete ou put signal for only a particular combination of multifrequency signals comprising first and second means responsive to different multifrequcncy signals and means responsive only to a given output signal from said first means to enable said second means, said second means output signal being the output signal for said apparatus andsaid first and second means each comprising apparatus that provides a respective certain output signal for only one particular applied muhifrequcncy signal comprising support means,.a plurality of light conducting fibers of varying resonant frequencies, means adapted to multifrequency signals and vibrate accordingly said support means, whereby said fibers vibrate at their resonant frequencies when the received signal contains frequency components at those frequencies, mask means for each fiber dimensioned to block or pass light emanating from its respective fiber when that fiber vibrates with an amplitude above and below the amount by which that iiber vibrates when said particular multifrequency signal is applied to said vibration means. and means responsive to produce a signal proportional to the light passing said mask means.

11. Apparatus responsive to produce a substantial output signal for only a particular combination of multifrequency signals comprising first and second means rcsponsive to different multifrequency signals and means responsive only to substantial output signals from said first means to enable said second means, said second means output signal being the output signal for said upparatus and said first and second means each comprising apparatus that provides a substantial output signal for only one particular applied multifrequency signal comprising support means, a plurality of light conducting fibers of varying resonant frequencies, means adapted to receive signals representing sounds and vibrate accordingly said support means, whereby said fibers vibrate at their resonant frequencies when the particular multifrequency signal contains frequency components at those frequencies, means for each fiber adapted to block light emanating therefrom when its respective fiber is stationary, transparencies for those fibers that move when par ticular multifrequency signal is applied to said vibration means which permit light from those fibers to pass therethrough, said transparencies getting progressively transparent at their extremities and being adapted to pass light from the fibers only so long as their respective instantaneous amplitudes of vibration are less than their peak vibratory amplitudes when vibrating in response to said particular multifrequency signal, and photoelectric means receiving the light passing through said transparencies and being responsive to produce a substantial output signal for only the particular sound representative signal.

12. Apparatus that provides a substantial output signal for only one particular multifrequency signal comprising support means, a plurality of light conducting fibers of varying resonant -frequencies, means adapted to receive signalsand vibrate accordingly said support means, whereby said fibers vibrate at their resonant frequencies when the multifrequency signal contains frequency components at those frequencies, means for each fiber adapted to block light emanating therefrom when its respective fiber is stationary, transparencies for those fibers that move when a signal representing said particular multifnequency signal is applied to said vibration means which permit light from those fibers to pass therethrough, said transparencies being progressively transparent from their centers to their extremities and being adapted to pass light from the fibers only so long as their respective instantaneous amplitudes of vibration are less than their peak vibratory amplitudes when vibrating in response to a signal representing said multifrequency signal, and means receiving the light passing through said transparencies and being responsive to produce a substantial. output signal for only the particular multifrequency signal.

13. Apparatus responsive to vibratory motion comprising a fiber capable of transmitting light from one of its ends, said fiber being adapted to receive light from a source of light signal producing means adapted to receive the light from said fiber end and produce a signal proportional thereto, mask means positioned between said fiber end ar d said signal producing means, and means for vibrating said fiber, said mask means being of a form that int'ereepts and passes the light from said fiber end depending on whether said fiber vibrates with an amplitude above or below a predetermined magnitude whereby the light transmitted from the end of the fiber falls periodically on said signal producing means,

14. Apparatus responsive to vibrating motion comprising a fiber capable of transmitting radiant energy from one of its ends, said fiber being adapted to receive radiant energy from a source of radiant energy, signal producing means adapted to receive the. radiant energy from said fiber end and produce a signal proportional thereto, mask means positioned between said fiber end and said signal producing means, and means for vibrating said fiber, said mask means being of a form that intercepts and passes the radiant energy from said fiber end depending on whether said fiber vibrates with an amplitude above or below a certain amount.

15. Apparatus responsive to vibration to transmit radiant energy from a source to an accumulator comprising a vi'bratable support; fibers, mounted thereon for vibration each at a resonant frequency, to receive energy from said source and to transmit said energy to said accumulator; and masking means for said fibers adapted to :be positioned and dimensioned to alternately intercept and pass radiant energy transmitted from respective fibers when those respective fibers are vibrated with amplitudes above and below predetermined amounts.

16. Apparatus responsive to vibration to transmit light energy from a source to an accumulator of light energy comprising a vibratable support; light conductive fibers, mounted thereon for vibration each at a resonant frequency, to receive light energy from said source and to transmit said energy to said accumulator; and masking means for said fibers adapted to be positioned and dimensioned to alternately intercept and pass light energy emanating from respective fibers when those respective fibers are vibrated with amplitudes above and below predetermined amounts.

17. Apparatus responsive to vibration to transmit light energy from a source to an accumulator of lightenergy comprising a vibratable support; light conductive fibers mounted as cantilevers thereon and having their respective free ends terminate in substantially tthe same plane; said support being shaped to provide said fibers with as sorted lengths and resonant frequencies; said fibers being adapted to receive energy from said source and to transmit said energy to said accumulator; and masking means for said fibers adapted to be positioned and dimensioned to alternately intercept and pass light energy transmitted from respective fibers when those respective fibers are vibrated with amplitudes above and :below predetermined amounts.

References Cited by the Examiner UNITED STATES PATENTS 2,476,445 7/49 Lacy 179-1 2,492,062 12/49 Potter 179--1 2,196,166 4/50 Bryce.

2,506,672 5/50 Kell et al. 178-6 2,575,910 11/51 Mathes 179-l 2,582,793 1/52 Perry 346-1 2,685,615 8/54 Biddulph et al. 1791 2,804,500 8/57 Giacoletto l79l 2,825,260, 3/58 OBrien 88-1 2,951,736 9/.60 Black 3461 3,036,153 5/62 Day 88-1 3,043,179 7/62 Dunn 88-1 ROBERT H. Rosa, Primary Examiner.

WILLIAM c. COOPER, Examiner. 

1. APPARATUS RESPONSIVE TO VIBRATORY MOTION COMPRISING A LIGHT CONDUCTIVE FIBER ONE END WHICH IS ADAPTED TO BE ILLUMINATED BY A SOURCE OF LIGHT, SIGNAL PRODUCING MEANS ADAPTED TO RECEIVE LIGHT FROM THE OTHER END OF SAID FIBER AND PRODUCE A SIGNAL PROPORTIONAL THERETO, MASK MEANS POSITIONED BETWEEN SAID FIBER''S OTHER END AND SAID SIGNAL PRODUCING MERANS, AND MEANS FOR VIBRATING SAID FIBER, SAID MASK MEANS BEING OF A FORM THAT INTERCEPTS AND PASSES THE LIGHT FROM SAID FIBER''S OTHER END DEPENDING ON WHETHER SAID FIBER VIBRATES WITH AN AMPLITUDE ABOVE OR BELOW A PERDETERMINED MAGNITUDE, WHEREBY THE LIGHT BEING EMITTED FROM SAID FIBER''S OTHER END MAY FALL PERIODICALLY ON SAID SIGNAL PRODUCING MEANS. 